Thousands Surround Home of Prime Minister Yingluck Shinawatra

BANGKOK—Large crowds of protesters spilled out onto the streets of Thailand's capital Sunday in a bid to force Prime Minister Yingluck Shinawatra to postpone new elections, throwing fresh uncertainty over the future of this Southeast Asian country's fragile democracy.

Demonstrators, many blowing whistles or waving red, white and blue Thai flags, swarmed outside Ms. Yingluck's home in the north of Bangkok and paralyzed traffic in the...